The invention relates to optical add/drop nodes, and more particularly to a method for designing optical add/drop nodes to maximize a result of known optical filter assignment algorithms in selecting optical filter cards for dropping predetermined wavelengths from an optical signal.
Optical add/drop nodes add and drop wavelengths in an optical network. An optical filter card acts as the vehicle for dropping the wavelengths. The optical filter card contains filters that drop selective wavelengths or groups of wavelengths. Regenerators are used at the add/drop nodes to add wavelengths. The regenerators contain laser light sources that can provide the desired light source for adding a wavelength. These components are typically found on a wavelength interface card (xe2x80x9cWICxe2x80x9d).
There are conventional types of optical filter cards that are customarily used in optical add/drop nodes. The first type drops four wavelengths at a time, while the second type drops six wavelengths at a time. Wavelengths that are not dropped optically bypass the add/drop node and continue toward their destinations over the optical network.
If a wavelength needs to be dropped at a given optical add/drop node, there must be an optical filter card that contains a filter for that wavelength. However, the optical filter card will likely also contain filters that drop other wavelengths. If the optical network design requires that the other additional wavelengths not terminate at the optical add/drop node, then the one or more of the other additional wavelengths require regeneration. Regeneration of the wavelengths is relatively costly since a new pair of WICs is required for every wavelength that is regenerated and such devices add to the cost of an optical network system.
Known filter assignment algorithms determine and assign the correct optical filter cards to utilize at each optical add/drop node in a manner such that the number of wavelength interface cards is minimized. A goal of the filter assignment algorithms is to choose optical fiber cards that drop as few non-terminating wavelengths as possible. As a result, such filter assignment algorithms maximize the number of wavelength bypasses at an optical add/drop node and minimize the number of wavelength regenerations; thus reducing the relative cost of the optical network.
The known filter assignment algorithms require the stipulation of a number of available optical filters. Each of the optical filters must filter different combinations of optical wavelengths so that the filter assignment algorithms have a variety of combinations to choose from in attempting to minimize the number of wavelength regenerations required.
Sets of optical filter cards must be designed that facilitate the filter assignment algorithm. Each optical filter card must contain a predetermined selection of wavelengths for the optical filter card to drop so that the filter assignment algorithm can find as efficient a solution as possible.
There is a need for a method of optical filter card design that facilitates a relatively efficient filter assignment algorithm solution resulting in a filter design that reduces a probability of unnecessary wavelength regenerations. The present invention is directed toward further solutions to address this existing need.
According to one example embodiment, a method for designing optical filter cards begins with providing a plurality of optical wavelength filters for filtering predetermined optical wavelengths disposed on a plurality of filter cards. The method continues with determining which of the optical wavelengths are filtered by each of the optical wavelength filters. A correlation is designated between optical wavelengths filtered by each of the optical wavelength filters. Additional optical filter correlations are then assigned to arrive at the designed optical filter card arrangement.
The step of providing can include determining a set of optical wavelengths requiring filtering in accordance with one embodiment of the present invention.
The determining step can be carried out by identifying specific wavelength filters to correspondingly filter said optical, according to a further aspect of the present invention.
The step of designating can include indicating a correlation between any wavelengths located on a same filter grouping.
The assigning step can include indicating a correlation between wavelengths of different filter groupings, such that distal wavelengths are grouped to form the correlation.
In accordance with a further embodiment of the present invention, the method can further include the step of manufacturing the optical filter cards having an arrangement of filters designed to minimize a need for regeneration of wavelengths unnecessarily dropped by the filter cards.
Still further aspects of the present invention include an optical filter node. The optical fiber node includes a plurality of optical filters arranged into a plurality of filter cards, wherein each of the plurality of optical filter cards is optimized to contain predetermined groupings of optical filters.
The optical filter node, according to one embodiment of the present invention, includes the predetermined groupings of optical filters such that each of the predetermined groupings of optical filters correlates distal optical wavelengths with each other.